In what kind of way do I have to look at it then? I tried the hex of the file, but that is nearly completely empty. When I look at the file with Audacity, to check if there actually is some kind of weak audio track, I see nothing.

Aaaah now that makes quite a lot more sense. At least that's a sound file with sound. Still I don't have a clue on how to approach this file. It looks like it's just an annoying sound and I can't really recognize a voice in it. A question:Are we ment to edit the file, so we can actually hear a password or something, or are we ment to find the password elsewhere, thus we don't hear it?